Device and method for carrying out spatially directed detection of an electroencephalogram

ABSTRACT

A method and arrangement for acquiring an electroencephalogram (EEG) are disclosed. A first set of electrodes is arranged to sense cortical signals generated primarily in a region of interest (ROI). A second set of electrodes are arranged to sense cortical signals generated inside and outside of the ROI. Individual signals sensed by each electrode of the first and second sets of electrodes are directed to a signal analyzer.

PRIORITY BASED ON FOREIGN FILING

This Application claims priority based on the following patentapplications filed in Germany: Application No. 100 58 128.5, having apriority date of Nov. 22, 2000; and Application No. 10145325.6, having apriority date of Sep. 14, 2001.

FIELD OF THE INVENTION

The invention relates generally to medical measurement and diagnostics,and more particularly, to measuring cortical signals generated in aparticular region of interest.

BACKGROUND OF THE INVENTION

The latest technology knows systems that capture the EEG with suitableelectrodes at predefined standardized positions and feed it to anamplifier. The disadvantageous effect is that the electrical activitycan only be captured from relatively large areas of the brain.

But in many medical problems of neurology, physiology or the functiondiagnostic the local brain activity of certain anatomical limited areasor centers is of more essential significance. A series of extensivesignal processing steps is necessary to capture the electrical activityof such areas and to free them from disturbances by the adjacent brainareas. For that the amplified EEG must be digitalized and afterwardsanalyzed in a computer.

One disadvantage of this procedure is that only an offline analysis ispossible. Therefore, this procedure can not be used in time criticalprocedures either.

SUMMARY OF THE INVENTION

One aspect of the invention is to supply a procedure and an arrangementin which the local electrical activity of a spatial limited brain areais captured and can be used for further processing and/or analysis. Atthe same time the affecting and disrupting fields from the adjacentbrain areas on the desired area to be examined shall be considerablysuppressed in their projection on the deviated potential.

According to one embodiment of the invention, it is intended with anarrangement for the spatial directed capturing of an electroencephalogram, in which electrodes are attached to the skull surface ofthe examined person, that

-   -   parts of the electrodes are arranged in such a way that they        capture the activity of the targeted cortical structure, and    -   other parts of the electrodes are arranged in such a way that        they capture the activity of the targeted cortical structure and        the activity of the surrounding areas and furthermore    -   an electronic evaluation circuit exists.

In an advantageous advancement of the arrangement according to oneembodiment of the invention, the electrodes are axial symmetricallyarranged around a reference electrode in an inner ring and an outerring.

Another aspect of the invention concerns a procedure for the spatialdirected capturing of the electro encephalogram, in which the electricalactivity is measured

-   -   over the targeted cortical structure as well as    -   over the targeted cortical structure and the adjacent area and    -   the received potentials are amplified and feed to an electrical        circuit.

In an advantageous advancement of the procedure according to oneembodiment of the invention, it is intended that the spatial directionalpattern for the capturing of the activity of a targeted corticalstructure is realized with signal processing algorithms.

The arrangement on hand, according to the invention, and the procedurebelonging to it is characterized in a way that the electrical activityof the targeted brain area is freed from disturbances simultaneously tothe EEG capturing. In traditional capturing methods this is onlypossible with the help of offline analysis, meaning with methods ofsignal processing that are based on several repetitions of themeasurement and are therefore clinically realized in a lot of cases withunacceptable delays.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates an EEG measurement arrangement according to oneembodiment of the present invention.

DETAILED DESCRIPTION

The arrangement illustrated in FIG. 1 can be used for examination of thevisual cortex. A double ring-shaped electrode pattern is attached on theskull surface over the visual cortex of the patient above the inion 4.The number of the used electrodes depends on the respective technicalequipment. They are axial symmetrically arranged around the referenceelectrode 1.

The electrodes of the inner electrode ring 2 are positioned directlyabove the ROI (region of interest—the target area). Its measurementshave to be selected depending on the known anatomical characteristics.

The electrodes of the outer electrode ring 3 additionally cover theactivity of the areas surrounding the ROI. The electrode potentials ofthe inner ring 2 and the outer ring 3 are amplified with common EEGamplifiers 5 and 6 and fed to the electronic block 7. The electricaldirection pattern of the electrode configuration and the interferencesuppression of adjacent brain areas is realized with a suitable analogand digital circuit technology as well as with an algorithm implementedin a micro controller or signal processor. The formed difference of theactivities of both brain volumes creates an almost undisturbed activityof the examined area (ROI). The examined person can already receivediagnostically relevant information during the reception of the brainpotentials.

1. A method of acquiring an electroencephalogram (EEG), the methodcomprising: attaching a first set of electrodes to a patient's head suchthat electrodes of the first set are arranged to sense cortical signalsgenerated primarily in a region of interest (ROI); attaching a secondset of electrodes to the patient's head such that electrodes of thesecond set are arranged to sense cortical signals generated inside andoutside of the ROI; attaching at least one reference electrode to thepatient's head, wherein the electrodes of the first set are arrangedsymmetrically about the reference electrode, and the electrodes of thesecond set are arranged symmetrically about the reference electrode; anddirecting individual signals sensed by each electrode of the first andsecond sets of electrodes to a signal analyzer.
 2. The method of claim1, wherein when the electrodes of the first and second sets areattached, the electrodes of the second set are arranged around theelectrodes of the first set.
 3. The method of claim 1, wherein when theelectrodes of the first and second sets are attached, the electrodes ofthe second set are arranged symmetrically about the electrodes of thefirst set.
 4. The method of claim 3, wherein the electrodes of the firstset are arranged in a pattern along a reference inner ring and theelectrodes of the second set are arranged in a pattern along a referenceouter ring that is concentric with the reference inner ring.
 5. Themethod of claim 1, and further comprising: processing each of theindividual electrical signals to produce an EEG based primarily onsignals generated in the ROI.
 6. The method of claim 5, wherein theprocessing is performed by the signal analyzer.
 7. The method of claim5, wherein the processing includes implementing a signal processingalgorithm.
 8. The method of claim 5, wherein the processing includessuppressing an BEG component that is caused by signals generated outsideof the ROI.
 9. The method of claim 8, further comprising: sensingcortical signals with the first and second sets of electrodes; whereinthe processing is performed during the sensing.